What unit is commonly used to measure the fuel value of food?

The commonly used unit to measure the fuel value of food is the kilocalorie. The kilocalorie, often referred to simply as "calorie" in dietary contexts, represents the amount of energy required to raise the temperature of one kilogram of water by one degree Celsius. This unit effectively conveys the energy content of food, which is crucial for understanding nutrition and dietary energy intake.

While the term "calorie" is frequently used in everyday language, it actually refers to a smaller unit of energy; one kilocalorie equals 1,000 calories. Thus, in the context of food and nutrition, the kilocalorie is the standard measurement because it conveniently reflects the energy provided by macronutrients like carbohydrates, proteins, and fats in amounts that align with typical dietary consumption.

The joule, another unit of energy, is more commonly used in scientific contexts but is less familiar and less practical for everyday discussions regarding food. The gram, on the other hand, measures mass, not energy. Therefore, when assessing the energy content of food, the kilocalorie is the most relevant and widely recognized unit.